Merge pull request scikit-learn-contrib#32 from tagomatech/tagomatech-patch-1

explicitly converted error message to string

Author: danielhomola

boruta/boruta_py.py

@@ -380,7 +380,7 @@ def _get_imp(self, X, y):
             self.estimator.fit(X, y)
         except Exception as e:
             raise ValueError('Please check your X and y variable. The provided'
-                             'estimator cannot be fitted to your data.\n' + e)
+                             'estimator cannot be fitted to your data.\n' + str(e))
         try:
             imp = self.estimator.feature_importances_
         except Exception: